Conventionally, there has been known a COB (Chip On Board) type of LED module (see JP 2014-170947 A (hereinafter referred to as Document 1) and JP 2008-140934 A (hereinafter referred to as Document 2)).
A COB type of LED module in Document 1 includes for example a resin board, an LED chip mounted on a first main surface of the resin board, a metal wiring, an electrode terminal, a resist, and a sealing member that is formed of resin containing phosphor. The metal wiring is formed on the first main surface of the resin board by patterning. The metal material for the metal wiring is copper for example. The resist is formed to cover the entire first main surface of the resin board, except for connection parts of the metal wiring, which are respectively connected with the LED chip and the electrode terminal. The resist is formed of white resin material.
A COB type of LED module in Document 2 includes: a device board; a white reflection layer, which the entire surface of the device board is covered with; a patterned circuit formed on the reflection layer; and an LED chip. The LED chip is bonded to the white reflection layer with an adhesive layer. Document 2 discloses that, for example, a silicone resin-based adhesive may be used as the adhesive layer.
Regarding the COB type of LED module in Document 1, when the LED chip and the resist are directly bonded to each other with an adhesive (die attach material) such as silicone resin, the bonding strength is low and therefore, the bonding reliability is desired to be improved.
Also regarding the COB type of LED module in Document 2, it is surmised that when the LED chip and the reflection layer are directly bonded to each other with an adhesive such as silicone resin, the bonding strength is low and therefore, the bonding reliability is desired to be improved.